Seamless steel pipes are classified into the following categories based on their intended applications:

GB/T 8162-1999 (Seamless Steel Pipes for Structural Purposes). Primarily used for general structural and mechanical applications. Representative materials (grades) include carbon steels No. 20 and No. 45; and alloy steels such as Q345, 20Cr, 40Cr, 20CrMo, 30-35CrMo, and 42CrMo.

GB/T 8163-1999 (Seamless Steel Pipes for Conveying Fluids). Primarily used for fluid conveyance pipelines in engineering projects and large-scale equipment. Representative materials (grades) include 20 and Q345.

GB 3087-1999 (Seamless Steel Pipes for Low- and Medium-Pressure Boilers). Primarily used for pipelines conveying low- and medium-pressure fluids in industrial and domestic boilers. Representative materials include 10 and 20 steel.

GB 5310-1995 (Seamless Steel Pipes for High-Pressure Boilers). Primarily used for high-temperature and high-pressure fluid transport headers and pipelines in power plant and nuclear power plant boilers. Representative grades include 20G, 12Cr1MoVG, and 15CrMoG.

GB 5312-1999 (Seamless Steel Pipes of Carbon and Carbon-Manganese Steel for Ships). Primarily used for Class I and II pressure-resistant pipes in ship boilers and superheaters. Representative grades include 360, 410, and 460 steel grades.

GB1479-2000 (Seamless Steel Pipes for High-Pressure Fertilizer Equipment). Primarily used for pipelines transporting high-temperature, high-pressure fluids in fertilizer equipment. Representative grades include 20, 16Mn, 12CrMo, and 12Cr2Mo.

GB 9948-1988 (Seamless Steel Pipes for Petroleum Cracking). Primarily used for boilers, heat exchangers, and fluid transport pipelines in petroleum refineries. Representative grades include 20, 12CrMo, 1Cr5Mo, and 1Cr19Ni11Nb.

GB 18248-2000 (Seamless Steel Pipes for Gas Cylinders). Primarily used for manufacturing various gas and hydraulic cylinders. Representative grades include 37Mn, 34Mn2V, and 35CrMo.

GB/T 17396-1998 (Hot-rolled Seamless Steel Pipes for Hydraulic Supports). Primarily used for manufacturing hydraulic supports, cylinders, and columns in coal mines, as well as other hydraulic cylinders and columns. Representative grades include 20, 45, and 27SiMn.

GB 3093-1986 (High-pressure seamless steel tubes for diesel engines). Primarily used for high-pressure fuel lines in diesel engine injection systems. These tubes are generally cold-drawn, with 20A being a representative grade.

GB/T 3639-1983 (Cold-drawn or cold-rolled precision seamless steel tubes). Primarily used for mechanical structures and carbon-compression equipment requiring high dimensional accuracy and surface finish. Representative grades include 20 and 45 steel.

GB/T 3094-1986 (Cold-drawn Seamless Steel Tubes and Special-shaped Tubes). Primarily used for manufacturing various structural components and parts, made from high-quality carbon structural steel and low-alloy structural steel.

GB/T 8713-1988 (Precision Inner Diameter Seamless Steel Tubes for Hydraulic and Pneumatic Cylinders). Primarily used for manufacturing cold-drawn or cold-rolled seamless steel tubes with precise inner diameter dimensions for hydraulic and pneumatic cylinder barrels. Representative grades include 20 and 45 steel.

GB 13296-1991 (Seamless Stainless Steel Tubes for Boilers and Heat Exchangers). Primarily used in chemical plants for boilers, superheaters, heat exchangers, condensers, and catalytic tubes. These tubes are designed to withstand high temperatures, high pressure, and corrosion. Representative grades include 0Cr18Ni9, 1Cr18Ni9Ti, and 0Cr18Ni12Mo2Ti.

GB/T 14975-1994 (Seamless Stainless Steel Pipes for Structural Applications). Primarily used for general structural applications (such as hotel and restaurant decoration) and mechanical structures in chemical plants, these pipes are resistant to atmospheric and acid corrosion and possess a certain level of strength. Representative grades include 0-3Cr13, 0Cr18Ni9, 1Cr18Ni9Ti, and 0Cr18Ni12Mo2Ti.

GB/T 14976-1994 (Seamless Stainless Steel Pipes for Fluid Conveyance). Primarily used for pipelines conveying corrosive media. Representative grades include 0Cr13, 0Cr18Ni9, 1Cr18Ni9Ti, 0Cr17Ni12Mo2, and 0Cr18Ni12Mo2Ti.

YB/T5035-1993 (Seamless Steel Pipes for Automotive Half-Shaft Sleeves). Primarily used for manufacturing seamless hot-rolled steel pipes made of high-quality carbon structural steel and alloy structural steel for automotive half-shaft sleeves and drive axle housing tubes. Representative grades include 45, 45Mn2, 40Cr, 20CrNi3A, etc.